[FLINK-12490][network] Introduce Input interface

flink-streaming-java/src/main/java/org/apache/flink/streaming/runtime/io/StreamTaskInput.java

@@ -0,0 +1,38 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http:https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.flink.streaming.runtime.io;
+
+import org.apache.flink.annotation.Internal;
+import org.apache.flink.runtime.io.NullableAsyncDataInput;
+import org.apache.flink.streaming.runtime.streamrecord.StreamElement;
+
+import java.io.Closeable;
+
+/**
+ * Basic interface for inputs of stream operators.
+ */
+@Internal
+public interface StreamTaskInput extends NullableAsyncDataInput<StreamElement>, Closeable {
+ int UNSPECIFIED = -1;
+
+ /**
+ * @return channel index of last returned {@link StreamElement}, or {@link #UNSPECIFIED} if
+ * it is unspecified.
+ */
+ int getLastChannel();
+}